How do I rename packed images? (Script)
Blender is able to do anything that you can do in python including renaming external files. I don't completely get what you are trying to do in detail, but you can rename textures in blender with 

import bpy
bpy.data.textures['29318291083'].name = '29318291083_Normal'


In python you can rename a file with

import os
os.rename('a.txt', 'b.kml')


If your textures are stored similar to .obj and its .mtl (I didn't bother checking tbh) you can just use python to open the file, search for the right lines and rename them. As renaming files and editing text are very common methods, Stackoverflow provides you with lots of help.